Previously, one has not systematically aimed at such a construction of a pre-tearing device for flake-dried pulp bale plate that the obtained pre-flour were as uniform and coarse as possible. This is why only some general solutions can be mentioned, such as chaff cutters (German Zerspaner), tearing devices for paper waste, etc. In these general solutions, remarkable machine powers are required, such as 50 kW. Frequently there is a bottom screen in general machines, such as in tearing devices for paper waste, for which reason there is often a considerable extent of dust at the machine because the material to be ground rolls around in the machine several times until it escapes through the bottom screen as having become sufficiently small.
A purpose of the present invention is to eliminate the above drawbacks and to provide a highly efficient pre-tearing device for bale plates. The pre-tearing device in accordance with the invention is mainly characterized in that the feeding device is arranged so as to feed the plates to be torn against the surface of the tearing cylinder in a direction that deviates from the perpendicular direction, and the spikes have been applied onto the cylindrical surface of the cylinder as two spirals rotating in opposite directions in relation to each other.